JPH02242521A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain composition of high dielectric constant and high insulation resistance, being excellent in quality Q, and of small temperature coefficient of electrostatic capacity by making the composition contain a specific amount of niobium oxide as auxiliary component against main components that the composition contains in such a manner that when an expression is given as xBaO-yTiO2-z(Re(1-c)Mec)O3/2, (x),(y) and (z) are in a specific mole ratio range. CONSTITUTION:The dielectric porcelain composition is made to contain niobium oxide as auxiliary component by 0. 3 to 8.0 parts by weight in Nb2O5 against main components that the composition contains in such a manner that when an expression is given as xBaO-yTiO2-z(Re(1-c)Mec)O3/2) (x+y+z=1.00; 0.01<=C<=0.20; Re is at least more than one kind of rare earth element selected among La, Pr, Nd and Sm; Me is at least more than one kind of rare earth elements selected from a group which does not include La, Pr, Nd and Sm), (x), (y)and (z) are in a mole ratio range surrounded by points (a) to (f) in the figure. The composition thereby has its dielectric constant, insulation resistance, insulation breakdown voltage enhanced, its quality Q largely improved and its temperature coefficient of electrostatic capacity reduced.

Description

[Detailed description of the invention] Industrial application field The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, greatly improves good dust Q, and has a small capacitance temperature coefficient, and is applicable to multilayer ceramic capacitors. The present invention relates to a dielectric ceramic composition that can prevent a decrease in capacitance and good dust Q when the thickness of the internal electrode is made thin, and can reduce variations in capacitance and good dust Q.

BACKGROUND OF THE INVENTION Conventionally, the following systems have been known as dielectric ceramic compositions that have high dielectric constants and insulation resistances, are excellent in dust Q by 3-7, and have small temperature coefficients of capacitance.

Problems to be solved by the Ba0-TiO2-Nd2o3 system BaO-TiO2-8m203 system However, these compositions, for example, 0.09 Ba0O,
A dielectric material with a composition ratio of 56TiO20, 35N d O3/2 is used, and the thickness of the palladium internal electrode is 4μ.
m, dielectric thickness 12 μm, internal electrode overlap dimension 1.2
When a multilayer ceramic capacitor with a laminated structure of 0.7 rmn and 19 dielectric layers is manufactured, the average value of capacitance is near 42 pF, the average value of quality Q is 8700, and the average value of temperature coefficient of capacitance is :NN35pp/°C, average value of insulation resistance: 6.0×10 Ω, average value of dielectric breakdown strength: 11 kv/m+++, which are not satisfactory values for insulation resistance and dielectric breakdown strength.

In order to reduce the cost of the spun multilayer ceramic capacitor and to prevent the occurrence of delamination, which is a structural defect inside the element body, the thickness of the radium internal electrode was reduced from 474 m to 2 μm. The average capacitance of a multilayer ceramic capacitor using a dielectric material with a composition ratio of The variation in capacitance becomes large, ranging from 256 to 713 pF. Furthermore, there was a problem in that the average value of the quality level Q was as low as 4,000, and the variation in the quality level Q was large, ranging from 600 to 8,800.

Means for Solving the Problems In order to solve these problems, the present invention provides the general formula x B
a Oy T 102 z (Re (1-c)
M ec ) When expressed as 0s72, (however, x+y
+z=1. oo.

0.01≦C≦0.20, Re is La, Pr,
Nd.

At least one rare earth element selected from Sm. M
e is at least one rare earth element selected from rare earth elements excluding La, Pr, Nd, and Sm).

Each point a, b, c, d where x+Y*z is represented below.

The main component consists of the molar ratio range surrounded by e, f, 5/, -
7 100 parts by weight, add niobium oxide as a subcomponent to Nb
The present invention proposes a dielectric ceramic composition characterized by containing 0.3 to 8.0 parts by weight in terms of 2o5.

Effects FIG. 1 is a ternary diagram showing the composition range of the main components of the composition according to the present invention.The reason for limiting the composition range of the main components will be explained from the viewpoint of force with reference to FIG. In short, sintering is extremely difficult in large areas. Furthermore, in region B, the quality Q decreases, making it impractical. Furthermore, the temperature coefficient of capacitance in the JD region is too steep on the negative side (6, -7), making it impractical.

In region E, the temperature coefficient of capacitance shifts to the positive direction, but the dielectric constant is small and it becomes difficult to use for practical use. Also, R
By selecting e from La, Pr, Nd, and Sm, La
, Pr , Nd , and Sm in that order, it is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant, and La.

The temperature coefficient of capacitance can be adjusted by using one type or a combination of Pr, Nd, and Sm.

Furthermore, as is clear from Tables 1 and 2, which will be described later, L
a, Pr, Nd, and Sm.

Substitution with at least one rare earth element selected from rare earth elements other than Pr, N+i, and Sm has the effect of significantly improving the quality Q, and the amount of substitution is 0.
If it is less than 0.01, there will be no substitution effect, and if it exceeds 0.20, the dielectric constant will decrease and become impractical.

Figure 2 is a graph showing the effect of the inclusion of the subcomponent Nb2O5 on the main component of the composition according to the present invention in terms of the properties of laminated ceramic material γ-7.See the graph for the reason for limiting the content range of Nb2O5. I will explain while doing so. As shown in Figure 2, the inclusion of Nb2O5 improves insulation resistance and dielectric breakdown strength, increases capacitance and good dust Q, and has the effect of reducing variations in capacitance and good dust Q. . Insulation resistance and dielectric breakdown strength are improved by the inclusion of Nb2O5, but if the content of Nb2O5 is less than 0.3 parts by weight per 100 parts by weight of the main component, the dielectric breakdown strength is not so high, and the capacitance and Since the good dust Q was low and the variation between the capacitance and the good dust Q was wide, it was excluded from the scope of this invention. On the other hand, if the content of Nb2O5 exceeds 8.0 parts by weight based on the main component, the good dust Q
, the insulation resistance decreases, the temperature coefficient of capacitance becomes large on the negative side, and the linearity of temperature change in capacitance is lost, making it impractical.

Example The present invention will be explained below using specific examples.

(Example 1) Starting materials include chemically high-purity BaCO3, TiO2゜La2O3, Pr6O11, Ha203, Sm2O3
, CaO2゜Gd2O3, Dy, , 03 and Nb2O
5 powder was weighed so as to have the composition ratio shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, wet-mixed, and then dehydrated and dried. This dry powder was placed in a high alumina crucible and heated to 1100℃ in air.
It was calcined for 2 hours. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, wet-pulverized, and then dehydrated and dried.

After adding an organic binder to this pulverized powder and making it homogeneous, the powder was sized through a 32-mesh sieve, and then molded using a mold and hydraulic press at a molding pressure of 1 ton/c4 to a diameter of 15 m.
m, thickness 0.4 mm. Next, the molded disk was placed in an alumina pod covered with zirconia powder, and dielectric porcelain having the composition ratio shown in Table 1 below was obtained in air.

The thickness and diameter of the dielectric ceramic disc thus obtained were measured, and the samples for measuring the dielectric constant, good dust Q, and capacitance temperature coefficient were prepared using silver electrodes on both sides of the dielectric ceramic disc. Baking, insulation resistance, and dielectric breakdown strength of 9 bases.

The measurement sample was placed 1 mm inside the outer periphery of the dielectric ceramic disk.
A part without a silver electrode was provided with a width of , and a silver electrode was baked onto it.

Then, the dielectric constant, good dust Q, and capacitance temperature coefficient are YH
Using a digital LCR meter model 4275A manufactured by Company P, the measurement temperature was 20°C and the measurement voltage was 1. ○Vrms was determined by measurement at a measurement frequency of 1 MHz. The temperature change in capacitance is -55℃, -25℃, 20℃, 85℃, 1
The capacitance at 25°C was measured to confirm linearity, and the temperature coefficient of capacitance was determined by the following equation using capacitances at 20°C and 85°C.

T O = (C-Go) /Go x 1 /65
106TC: Capacitance temperature coefficient (ppm/T;) Go
: Capacitance at 20°C (pF) C: Capacitance at 85°C (pF) The dielectric constant was calculated using the following formula.

K −= 143.8 X Go X t/D2K:
Dielectric constant CO: Capacitance (pF) at 2Q0C D = Diameter of dielectric porcelain (rLrIn) to 1/l: Thickness of dielectric porcelain (mm) Furthermore, the insulation resistance is determined by the model of HR meter manufactured by YHP. 4
329A, the measurement voltage was 50V, and the measurement time was 1 minute.

The dielectric breakdown strength was determined by using a PH335 type 13 high voltage power supply made by Kikusui Electronics Co., Ltd., placing the sample in silicone oil, and calculating the dielectric breakdown voltage at a boost rate of 50 V/sec. Divided by the thickness to obtain the dielectric breakdown strength of 1 division.

The test conditions are also shown in Table 1, and the test results are shown in Table 2 below.
Shown in the table.

(Left below) 11＼-7 13＼-7 (Example 2) Chemically high-purity BaCO3, Tie2N are used as starting materials.
d203. Using CeO2 and Nb2O5 powder, main component 0.09 BaO-0,56T102-0.35C
(Nd03/2) 0.95 ("02) o, for o51 ・Nb2O5 0, 0.1, 0.3, O,
E5, 1.0, 5.0', 8.0.

A calcined pulverized powder containing 1o, owtq6 is prepared in the same manner as in Example 1. However, Nb2O content is 0°0.
1,10. c) wt% is outside the scope of this invention and 0
．． 3, 0.5, 1.0, 5.0, 8. Owt%
is within the scope of this invention.

An organic binder, a plasticizer/dispersant, and an organic solvent were added to this calcined and pulverized powder, and mixed in a polyethylene pot equipped with alumina balls to prepare a slurry. After mixing, 3
It was filtered using a 00 mesh nylon cloth. The filtered slurry was passed through a doctor blade, and a sheet was formed on a polyester film that had been subjected to mold release treatment so that the dielectric thickness after sintering was 12 μm.

Next, 10 sheets of 14 sheets peeled from the polyester film were laminated on a support stand. On top of this, Shoei Chemical (
ML3724 (Table Internal Electrode Palladium Pace Co., Ltd.) was screen printed so that the internal electrode thickness after sintering was 2 μm, and dried. On top of this, a sheet 1-1 peeled from a polyester film was laminated. On top of this, internal electrode palladium paste was printed with the printing position shifted so that the internal electrode shape dimensions after sintering were 1.2 am x O, 7 mm, and after drying, sheet 1 was peeled off from the polyester film. The sheets were stacked. These operations were repeated until the number of dielectric layers reached 19. On top of this, 1 to 10 sheets of sheets peeled from the polyester film were laminated. After sintering this laminate, it was cut into a laminate ceramic capacitor having a laminate structure with internal electrode dimensions of 1.2 mm x 0.7 m, dielectric thickness of 12 μm, and 19 dielectric layers. This cut sample was placed in an alumina case covered with zirconia powder and heated at 350'ct from room temperature in air for 55 minutes.
Increase temperature at °C/hr, from 350 °C to 100 °C/hr
After heating at 1270℃ for 2 hours, 100℃/hr
The temperature in the room was lowered to 15 months. Next, the fired sample is placed in a polyethylene bot attached to the inside of a water-resistant sundry bar with pure water, and the polyethylene bot is rotated to polish the surface of the fired sample to remove the internal electrode portion that will be connected to the external electrode. It was fully exposed. This sample was taken out of the polyethylene bottle and dried, and a silver external electrode was baked onto the exposed part of the internal electrode to make it conductive with the internal electrode, producing a multilayer ceramic capacitor.

The capacitance, quality Q, temperature coefficient of capacitance, insulation resistance, and dielectric breakdown strength of these samples were determined by measurements under the same conditions as in Example 1. In addition, the laminated structure can be confirmed by optical microscopic observation of a polished cross section of the multilayer ceramic capacitor in the length and width directions at a magnification of 100 for internal electrode overlap dimensions, and at a magnification of 400 for the dielectric thickness and internal electrode thickness. I asked for it.

The measurement results are shown in FIG.

In addition, in the method for manufacturing dielectric ceramic in the example, Ba
CO3, TiO2, La2O5, Pr6Cm +Nd2
06. S+n205. CeO2, Gd2O3, D
y,,O.

Although BaT10 and Nb2O5 were used, it is not limited to this method, and BaT10
By heating in air, compounds such as 3, carbonates, hydroxides, etc., BaO, TiO□・La2O3, Pr
6O11,Nd2O5,Sm,,05. CeO2゜G
c1206. 7205 and Nb2O5, properties comparable to those of the examples can be obtained.

Further, even if the main component is calcined in advance and the subcomponents are added, properties comparable to those of the examples can be obtained.

In addition, titanium dioxide, an industrial raw material commonly used for dielectric ceramics, such as titanium dioxide K A-10 manufactured by Titan Industries Co., Ltd. and titanium dioxide FA manufactured by Furukawa Mining Co., Ltd.
-65W contains up to 0.45 parts by weight of Nb2o5, but even if these titanium dioxides are used to make dielectric porcelain as the main component, Nb2o5 is contained per 100 parts by weight of the main component.
The content of O5 is at most 0.23 parts by weight, which is outside the scope of this invention, but the content of Nb2 in titanium dioxide, an industrial raw material, is
By considering the amount of O and incorporating Nb2O, which is less than 17 pages, it is possible to obtain properties comparable to those of the examples.

In addition, in the examples, Ce, Dy, and Gd were explained as rare earth elements Me other than La, Pr, Nd, and Sm, but characteristics comparable to those in the examples can be obtained even if other rare earth elements are used. .

In addition to the basic composition mentioned above, Sin, , Mn
O2°Fe2o3. Salts, oxides, etc., which are generally considered to be fluxes, such as ZnO, can also be added to the extent that they do not impair the properties.

Effects of the Invention As described above, according to the present invention, the dielectric constant, insulation resistance, and dielectric breakdown voltage are high, the quality Q is greatly improved, the temperature coefficient of capacitance is small, and it is suitable for use in multilayer ceramic capacitors. By reducing the thickness of the internal electrode, it is possible to prevent the capacitance and quality Q from decreasing when the thickness of the internal electrode is made thinner, and to reduce variations in the capacitance and quality Q.
The cost of multilayer ceramic capacitors can be reduced, and the occurrence of delamination, which is an internal structural defect, can be prevented. Because the dielectric breakdown voltage is high,
By reducing the thickness of the dielectric layer, it is possible to miniaturize products and increase capacity.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram explaining the composition range of the main components of the composition according to the present invention, and FIG. 2 is a ternary diagram illustrating the composition range of the main components according to the present invention.
BaO-0,56TiO2-0,35 [(NdOs/
2) The effect of the addition of the subcomponent Nb2O5 on o95 (Ce02)0.05] was evaluated using a multilayer ceramic having a laminated structure with dielectric thickness: 12 μm, internal electrode overlap dimension: 1.2 m + nX0.7 mm, and number of dielectric layers = 19. It is a graph showing the electrical characteristics of a capacitor. Name of agent: Patent attorney Shigetaka Awano and 1 other person (7
Σノ■Shang Pak W (悂ψ/Ha Takumi) Kibyo Shiromachi Kenran

Claims (1)

[Claims] General formula xBaO-yTiO_2-z(Re_(_1_-_C_
)Me_C)O_3_/_2, (where x
+y+z=1.00, 0.01≦C≦0.20, Re is at least one rare earth element selected from La, Pr, Nd, and Sm. Me is at least one rare earth element selected from rare earth elements excluding La, Pr, Nd, and Sm). For 100 parts by weight of the main component consisting of the range of molar ratios where x, y, z are surrounded by each point a, b, c, d, e, f shown below, niobium oxide is converted to Nb_2O_5 as a subcomponent. A dielectric ceramic composition characterized in that it contains 0.3 to 8.0 parts by weight. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼